1. Field of the Invention
This invention relates to computer systems and in particular to such systems capable of displaying images, as upon a cathode ray tube, in accordance with any of a variety of programs as stored upon a low-cost, limited capacity storage unit such as a tape cassette, and capable of viewer interaction to control the selection of the displayed image as well as to store data upon the storage unit.
2. State of the Prior Art
There is presently known in the art the adaptation of a television receiver to play a number of games, e.g. a paddle-type game where one or more players operates control sticks to cause the image of a ball to move repeatedly from side to side as the players manipulate the displayed paddle to intercept the ball and to return it to the opposing player. Typically, these systems are implemented in hardware game circuitry including, for example, a power supply and an oscillator producing a master timing signal for the TV display system. A horizontal sync circuit provides a clock frequency into clock submultiples, which are variously combined to generate reset, blanking and sync signals. A vertical sync circuit provides a horizontal reset into vertical submultiples for combination into vertical reset, blanking and sync signals. The two sync signals usually are combined into a composite sync signal that synchronizes the data display of the receiver's cathode ray tube (CRT) with the game circuitry. A stationary image is displayed upon the CRT that makes up the background as generated by a playfield display section. The remaining images are generated by an object display circuit and moved around at various speeds by horizontal deflection and motion circuits, which are coupled to the aforementioned sync circuits. A score occurs when a ball is not returned and an appropriate signal is generated and applied to a storage circuit which counts each such unreturned ball and controls a display circuit to present the correct scores upon the CRT. Typically, there also is included a game length circuit in the form of a timer or a score counting circuit that has a time limit or the number of points scored, to disable the game circuitry. Further, a sound circuit is provided including an appropriate amplifier and speaker, whereby appropriate game-like sounds, e.g. the ping and pong of a ping-pong ball striking a paddle, are provided upon the occurrence of a ball hitting the displayed paddle and also to indicate the scoring of a point.
A variety of such games has been implemented by integrated circuits and are adapted to display, as upon a television CRT, games such as tennis, hockey featuring a goalie and a forward for each side, squash, practice one-man squash, and a variety of rifle-shooting games. As development of such games has proceeded, the control circuitry has become increasingly sophisticated, whereby the difficulty of the games may be varied. For example, the size of the bat or racket, as well as the ball speed, may be changed. Further, the angles of return from the paddle or racket may be changed to increase the difficulty of the game. In addition, ball service may be automatic or manually-controlled, whereby the players can control how the on-screen generated ball is put into play after each point is scored. In a rifle-shooting game, a manual control in the game circuitry initiates the movement of a target upon the CRT screen, and a rifle in the form of a light source is aimed at the target. When the rifle's trigger is pulled, a shot counter in incremented. If the rifle is on-target, the rifle light source as focused upon a photocell inidicates a hit and the output from the photocell is applied to a hit counter which is incremented, and thereafter a hit noise is generated and the target is blanked for the duration of the hit signal. After fifteen shots, the score appears on the screen to indicate the total shots and the number of hits.
In more recent developments, such games have been adapted for display upon color CRT's, and have included large-scale integrated circuits that first process the color or chroma information to be applied in a format similar to that of a broadcasted color TV signal. Basically, the color signals are treated as two vectors defined by the blue (B-Y luminance) and red (R-Y luminance) as provided by an integrated circuit chip that includes a series of field-effect transistor switches and a resistor matrix. The integrated circuit chip also includes logic that is programmed to produce appropriate colors in any portion of a line then being scanned. By controlling the switching matrix, two separate voltages are produced, corresponding to the B-Y and R-Y vectors that are programmed to produce a desired color signal. The two vectors are applied to a chroma modulator having a stable color transmission frequency provided by a 3.58 MHz crystal oscillator; in this manner, the color signal is phase-modulated and transmitted to the color CRT receiver.
It is contemplated that most of the above-described games are implemented by "hard-wired circuitry", taking the form of large-scale integrated circuits. The level of their sophistication is relatively low and permits only a limited amount of adaptability as determined by the configuration of the game's control circuitry. In this regard, it is contemplated that presently-available microprocessors could well be adapted to such game systems whereby a variety of more sophisticated games could be played with circuitry implemented by a microprocessor. At present, there is available such a game including a microprocessor, a static memory interface, a read-only memory (ROM) and a random-access memory (RAM) including a light-emitting diode display whereby a game of chess may be displayed. In addition, such a game may be readily adapted to show the board and chess pieces upon a conventional CRT display. By the use of the increased sophisication provided by the microprocessor, each player in the game is able to control the move of each piece by pressing control keys specifying and entering the "from" and the "to" squares in terms of ranks and files, giving the coordinates of each square. The counter move is determined by the microprocessor and is initiated by the player pressing the designated key, thus instructing the processor to analyze the move and to respond thereto. Significantly, the degree of complexity in responding to the player's move may be changed to a variety of levels. The higher the level, the more time the processor requires to respond.
In addition, a microprocessor has been adapted to be used in a "gunfight" game wherein two figures are displayed on the CRT screen and the players try to shoot each other by viewer input to maneuver the displayed image on the screen and pressing trigger controls. In such a game, the microprocessor is adapted for use with a CRT, by storing image data indicative of the gunfighter as well as background images, in a relatively large random-access memory and reading out the image data, while conventional horizontal deflection circuits generate the raster of the CRT. In an illustrative format, the pattern on the screen is composed of 224 horizontal lines, each being 256 dots long, whereby the RAM holds 224.times.256 bits of information, which are sequentially read out during the scanning process. Further, it is contemplated that the game that the program plays may be changed by storing game information upon a storage means in the form of a cartridge or tape cassette, thus providing flexibility with respect to a fixed game as implemented by hard-wire LSI circuits.
The above-described system, whether implemented by conventional circuitry, LSI circuits or microprocessors, have been limited to a great extent to playing games, even though at increasing levels of sophistication. It is contemplated by this invention to provide a computer system illustratively implemented by a microprocessor, that is capable of many different functions, only one of which relates to playing a game, involving images to be displayed upon a cathode ray tube. In this regard, there are many applications besides the playing of games, where such systems would have application, such as a "home computer", capable of performing many functions within the home. For example, a computer could be used to store information such as Christmas lists or telephone numbers. A further contemplated application of such a system would be as an educational device that could be used in schools or in the home to teach children or adults. In addition, such a system could be used in business, for recordkeeping or for teaching purposes. The applications for such systems are limitless and the introduction of flexibility into the previously game-oriented systems would permit the basic components of these systems to be used in a great number of different applications.